[ARM] 3881/4: xscale: clean up cp0/cp1 handling
XScale cores either have a DSP coprocessor (which contains a single
40 bit accumulator register), or an iWMMXt coprocessor (which contains
eight 64 bit registers.)
Because of the small amount of state in the DSP coprocessor, access to
the DSP coprocessor (CP0) is always enabled, and DSP context switching
is done unconditionally on every task switch. Access to the iWMMXt
coprocessor (CP0/CP1) is enabled only when an iWMMXt instruction is
first issued, and iWMMXt context switching is done lazily.
CONFIG_IWMMXT is supposed to mean 'the cpu we will be running on will
have iWMMXt support', but boards are supposed to select this config
symbol by hand, and at least one pxa27x board doesn't get this right,
so on that board, proc-xscale.S will incorrectly assume that we have a
DSP coprocessor, enable CP0 on boot, and we will then only save the
first iWMMXt register (wR0) on context switches, which is Bad.
This patch redefines CONFIG_IWMMXT as 'the cpu we will be running on
might have iWMMXt support, and we will enable iWMMXt context switching
if it does.' This means that with this patch, running a CONFIG_IWMMXT=n
kernel on an iWMMXt-capable CPU will no longer potentially corrupt iWMMXt
state over context switches, and running a CONFIG_IWMMXT=y kernel on a
non-iWMMXt capable CPU will still do DSP context save/restore.
These changes should make iWMMXt work on PXA3xx, and as a side effect,
enable proper acc0 save/restore on non-iWMMXt capable xsc3 cores such
as IOP13xx and IXP23xx (which will not have CONFIG_CPU_XSCALE defined),
as well as setting and using HWCAP_IWMMXT properly.
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ce00c57..7be67ef 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -374,6 +374,14 @@
source arch/arm/mm/Kconfig
+config IWMMXT
+ bool "Enable iWMMXt support"
+ depends CPU_XSCALE || CPU_XSC3
+ default y if PXA27x
+ help
+ Enable support for iWMMXt context switching at run time if
+ running on a CPU that supports it.
+
# bool 'Use XScale PMU as timer source' CONFIG_XSCALE_PMU_TIMER
config XSCALE_PMU
bool
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 1320a0e..ab06a86 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -24,7 +24,9 @@
obj-$(CONFIG_CRUNCH) += crunch.o crunch-bits.o
AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
-obj-$(CONFIG_IWMMXT) += iwmmxt.o iwmmxt-notifier.o
+obj-$(CONFIG_CPU_XSCALE) += xscale-cp0.o
+obj-$(CONFIG_CPU_XSC3) += xscale-cp0.o
+obj-$(CONFIG_IWMMXT) += iwmmxt.o
AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt
ifneq ($(CONFIG_ARCH_EBSA110),y)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index bd623b7..2db42b1 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -589,10 +589,6 @@
strex r5, r4, [ip] @ Clear exclusive monitor
#endif
#endif
-#if defined(CONFIG_CPU_XSCALE) && !defined(CONFIG_IWMMXT)
- mra r4, r5, acc0
- stmia ip, {r4, r5}
-#endif
#if defined(CONFIG_HAS_TLS_REG)
mcr p15, 0, r3, c13, c0, 3 @ set TLS register
#elif !defined(CONFIG_TLS_REG_EMUL)
@@ -602,11 +598,6 @@
#ifdef CONFIG_MMU
mcr p15, 0, r6, c3, c0, 0 @ Set domain register
#endif
-#if defined(CONFIG_CPU_XSCALE) && !defined(CONFIG_IWMMXT)
- add r4, r2, #TI_CPU_DOMAIN + 40 @ cpu_context_save->extra
- ldmib r4, {r4, r5}
- mar acc0, r4, r5
-#endif
mov r5, r0
add r4, r2, #TI_CPU_SAVE
ldr r0, =thread_notify_head
diff --git a/arch/arm/kernel/iwmmxt-notifier.c b/arch/arm/kernel/iwmmxt-notifier.c
deleted file mode 100644
index 0d1a1db..0000000
--- a/arch/arm/kernel/iwmmxt-notifier.c
+++ /dev/null
@@ -1,63 +0,0 @@
-/*
- * linux/arch/arm/kernel/iwmmxt-notifier.c
- *
- * XScale iWMMXt (Concan) context switching and handling
- *
- * Initial code:
- * Copyright (c) 2003, Intel Corporation
- *
- * Full lazy switching support, optimizations and more, by Nicolas Pitre
- * Copyright (c) 2003-2004, MontaVista Software, Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-#include <linux/module.h>
-#include <linux/types.h>
-#include <linux/kernel.h>
-#include <linux/signal.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <asm/thread_notify.h>
-#include <asm/io.h>
-
-static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t)
-{
- struct thread_info *thread = t;
-
- switch (cmd) {
- case THREAD_NOTIFY_FLUSH:
- /*
- * flush_thread() zeroes thread->fpstate, so no need
- * to do anything here.
- *
- * FALLTHROUGH: Ensure we don't try to overwrite our newly
- * initialised state information on the first fault.
- */
-
- case THREAD_NOTIFY_RELEASE:
- iwmmxt_task_release(thread);
- break;
-
- case THREAD_NOTIFY_SWITCH:
- iwmmxt_task_switch(thread);
- break;
- }
-
- return NOTIFY_DONE;
-}
-
-static struct notifier_block iwmmxt_notifier_block = {
- .notifier_call = iwmmxt_do,
-};
-
-static int __init iwmmxt_init(void)
-{
- thread_register_notifier(&iwmmxt_notifier_block);
-
- return 0;
-}
-
-late_initcall(iwmmxt_init);
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 29efc9f..6f12d26 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -357,9 +357,6 @@
#ifndef CONFIG_VFP
elf_hwcap &= ~HWCAP_VFP;
#endif
-#ifndef CONFIG_IWMMXT
- elf_hwcap &= ~HWCAP_IWMMXT;
-#endif
cpu_proc_init();
}
diff --git a/arch/arm/kernel/xscale-cp0.c b/arch/arm/kernel/xscale-cp0.c
new file mode 100644
index 0000000..180000b
--- /dev/null
+++ b/arch/arm/kernel/xscale-cp0.c
@@ -0,0 +1,179 @@
+/*
+ * linux/arch/arm/kernel/xscale-cp0.c
+ *
+ * XScale DSP and iWMMXt coprocessor context switching and handling
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <asm/thread_notify.h>
+#include <asm/io.h>
+
+static inline void dsp_save_state(u32 *state)
+{
+ __asm__ __volatile__ (
+ "mrrc p0, 0, %0, %1, c0\n"
+ : "=r" (state[0]), "=r" (state[1]));
+}
+
+static inline void dsp_load_state(u32 *state)
+{
+ __asm__ __volatile__ (
+ "mcrr p0, 0, %0, %1, c0\n"
+ : : "r" (state[0]), "r" (state[1]));
+}
+
+static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t)
+{
+ struct thread_info *thread = t;
+
+ switch (cmd) {
+ case THREAD_NOTIFY_FLUSH:
+ thread->cpu_context.extra[0] = 0;
+ thread->cpu_context.extra[1] = 0;
+ break;
+
+ case THREAD_NOTIFY_SWITCH:
+ dsp_save_state(current_thread_info()->cpu_context.extra);
+ dsp_load_state(thread->cpu_context.extra);
+ break;
+ }
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block dsp_notifier_block = {
+ .notifier_call = dsp_do,
+};
+
+
+#ifdef CONFIG_IWMMXT
+static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t)
+{
+ struct thread_info *thread = t;
+
+ switch (cmd) {
+ case THREAD_NOTIFY_FLUSH:
+ /*
+ * flush_thread() zeroes thread->fpstate, so no need
+ * to do anything here.
+ *
+ * FALLTHROUGH: Ensure we don't try to overwrite our newly
+ * initialised state information on the first fault.
+ */
+
+ case THREAD_NOTIFY_RELEASE:
+ iwmmxt_task_release(thread);
+ break;
+
+ case THREAD_NOTIFY_SWITCH:
+ iwmmxt_task_switch(thread);
+ break;
+ }
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block iwmmxt_notifier_block = {
+ .notifier_call = iwmmxt_do,
+};
+#endif
+
+
+static u32 __init xscale_cp_access_read(void)
+{
+ u32 value;
+
+ __asm__ __volatile__ (
+ "mrc p15, 0, %0, c15, c1, 0\n\t"
+ : "=r" (value));
+
+ return value;
+}
+
+static void __init xscale_cp_access_write(u32 value)
+{
+ u32 temp;
+
+ __asm__ __volatile__ (
+ "mcr p15, 0, %1, c15, c1, 0\n\t"
+ "mrc p15, 0, %0, c15, c1, 0\n\t"
+ "mov %0, %0\n\t"
+ "sub pc, pc, #4\n\t"
+ : "=r" (temp) : "r" (value));
+}
+
+/*
+ * Detect whether we have a MAC coprocessor (40 bit register) or an
+ * iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000
+ * into a coprocessor register and reading it back, and checking
+ * whether the upper word survived intact.
+ */
+static int __init cpu_has_iwmmxt(void)
+{
+ u32 lo;
+ u32 hi;
+
+ /*
+ * This sequence is interpreted by the DSP coprocessor as:
+ * mar acc0, %2, %3
+ * mra %0, %1, acc0
+ *
+ * And by the iWMMXt coprocessor as:
+ * tmcrr wR0, %2, %3
+ * tmrrc %0, %1, wR0
+ */
+ __asm__ __volatile__ (
+ "mcrr p0, 0, %2, %3, c0\n"
+ "mrrc p0, 0, %0, %1, c0\n"
+ : "=r" (lo), "=r" (hi)
+ : "r" (0), "r" (0x100));
+
+ return !!hi;
+}
+
+
+/*
+ * If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we
+ * disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy
+ * switch code handle iWMMXt context switching. If on the other
+ * hand the CPU has a DSP coprocessor, we keep access to CP0 enabled
+ * all the time, and save/restore acc0 on context switch in non-lazy
+ * fashion.
+ */
+static int __init xscale_cp0_init(void)
+{
+ u32 cp_access;
+
+ cp_access = xscale_cp_access_read() & ~3;
+ xscale_cp_access_write(cp_access | 1);
+
+ if (cpu_has_iwmmxt()) {
+#ifndef CONFIG_IWMMXT
+ printk(KERN_WARNING "CAUTION: XScale iWMMXt coprocessor "
+ "detected, but kernel support is missing.\n");
+#else
+ printk(KERN_INFO "XScale iWMMXt coprocessor detected.\n");
+ elf_hwcap |= HWCAP_IWMMXT;
+ thread_register_notifier(&iwmmxt_notifier_block);
+#endif
+ } else {
+ printk(KERN_INFO "XScale DSP coprocessor detected.\n");
+ thread_register_notifier(&dsp_notifier_block);
+ cp_access |= 1;
+ }
+
+ xscale_cp_access_write(cp_access);
+
+ return 0;
+}
+
+late_initcall(xscale_cp0_init);
diff --git a/arch/arm/mach-pxa/Kconfig b/arch/arm/mach-pxa/Kconfig
index 03d07ca..9e3d0bd 100644
--- a/arch/arm/mach-pxa/Kconfig
+++ b/arch/arm/mach-pxa/Kconfig
@@ -13,12 +13,10 @@
config MACH_LOGICPD_PXA270
bool "LogicPD PXA270 Card Engine Development Platform"
select PXA27x
- select IWMMXT
config MACH_MAINSTONE
bool "Intel HCDDBBVA0 Development Platform"
select PXA27x
- select IWMMXT
config ARCH_PXA_IDP
bool "Accelent Xscale IDP"
@@ -53,7 +51,6 @@
config PXA_SHARPSL_27x
bool "Sharp PXA270 models (SL-Cxx00)"
select PXA27x
- select IWMMXT
endchoice
@@ -129,11 +126,6 @@
help
Select code specific to PXA27x variants
-config IWMMXT
- bool
- help
- Enable support for iWMMXt
-
config PXA_SHARP_C7xx
bool
select PXA_SSP
diff --git a/arch/arm/mach-pxa/pm.c b/arch/arm/mach-pxa/pm.c
index 2112c41..b4d8276 100644
--- a/arch/arm/mach-pxa/pm.c
+++ b/arch/arm/mach-pxa/pm.c
@@ -83,7 +83,8 @@
#ifdef CONFIG_IWMMXT
/* force any iWMMXt context to ram **/
- iwmmxt_task_disable(NULL);
+ if (elf_hwcap & HWCAP_IWMMXT)
+ iwmmxt_task_disable(NULL);
#endif
/* preserve current time */
diff --git a/arch/arm/mm/proc-xscale.S b/arch/arm/mm/proc-xscale.S
index 906e9de..cc1004b 100644
--- a/arch/arm/mm/proc-xscale.S
+++ b/arch/arm/mm/proc-xscale.S
@@ -491,12 +491,7 @@
mcr p15, 0, ip, c7, c7, 0 @ invalidate I, D caches & BTB
mcr p15, 0, ip, c7, c10, 4 @ Drain Write (& Fill) Buffer
mcr p15, 0, ip, c8, c7, 0 @ invalidate I, D TLBs
-#ifdef CONFIG_IWMMXT
- mov r0, #0 @ initially disallow access to CP0/CP1
-#else
- mov r0, #1 @ Allow access to CP0
-#endif
- orr r0, r0, #1 << 6 @ cp6 for IOP3xx and Bulverde
+ mov r0, #1 << 6 @ cp6 for IOP3xx and Bulverde
orr r0, r0, #1 << 13 @ Its undefined whether this
mcr p15, 0, r0, c15, c1, 0 @ affects USR or SVC modes
@@ -909,7 +904,7 @@
b __xscale_setup
.long cpu_arch_name
.long cpu_elf_name
- .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP|HWCAP_IWMMXT
+ .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP
.long cpu_pxa270_name
.long xscale_processor_functions
.long v4wbi_tlb_fns